Ultraminer Settings for 280x(Sapphire R9 280X 3GB GDDR5 OC VAPOR-X) With 4GB system Ramsetx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
cgminer.exe --scrypt-jane --sj-nfmin 4 --sj-nfmax 30 --sj-time 1388361600 -o -u -p --lookup-gap 3 --thread-concurrency 36864 -g 2 -I 12 -w 256 --gpu-memclock 1500 --gpu-engine 1052 --no-submit-stale
This gave me No HW error and a hashrate between 40-45 khs
When I upgraded my system ram from 4 to 12 GB ram, YacMiner became more usefull
Yacminer Settings for 280x(Sapphire R9 280X 3GB GDDR5 OC VAPOR-X) With 12GB system Ramsetx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
yacminer.exe --scrypt-chacha -o -u -p --worksize 128 -g 1 --lookup-gap 3 --buffer-size 2590 -R 8000 --temp-cutoff 85 --nfmin 4 --nfmax 30 --starttime 1388361600 --gpu-memclock 1500 --gpu-engine 1025 --no-submit-stale
This gives me a hashrate of 55-60 khs without HW errors,
*** If you get HW error lower -R to 7680Download yacminer here :
https://github.com/Thirtybird/YACMiner/releasesMore Ram gives you better Results.. With a upgrade from 4 to 12 GB ram I gained 30-40% more hashpower
If these settings helped you out you can always make a little donation

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